Effects Of Planting Pattern On Photosynthetic Characters And Nutrient Absorption Of Soybean

Since the 21st century,the development of sustainable agriculture has got universal attention,excessive fertilization had lead to many environmental problems,and the use of high-yield crop varieties combined with appropriate planting patterns is an important way to increase crop yield.Some studies have found that using uniform planting can increase soybean yield,but the results were different with different variety and climate.In addition,there are few studies on the physiological mechanism of how to increase soybean yield by uniform planting pattern.Therefore,this study takes“Dong nong 52”,the main planting high-yield soybean variety in Heilongjiang Province,as the research material.The experiment include six treatments:row planting in low density（RL）,row planting in medium density（RM）,row planting in high density（RH）,uniform planting in low density（UL）,uniform planting in medium density（UM）and uniform planting in high density（UH）.From Four-leaf stage（V4）,five-leaf stage（V5）,initial pod stage（R3）,pod stage（R4）,seed-filling stage（R6）,and ripening stage（R8）,we studied the dynamics of dry matter accumulation,photosynthetic characteristics and nutrient absorption of soybean and the difference of soybean yield and quality in different planting patterns（uniform and traditional row pattern）and three different densities(25（low）,36（medium）,49（high）×10,000 seeds hm^-2),This study will contributed to better clarify how uniform planting promoted soybean yield and provide theoretical basis for the suitable planting pattern and planting density for soybean in the first accumulated temperate zone of Heilongjiang Province.The results are as follows:（1）The effect of planting pattern on chlorophyll content of soybean were significant,during the whole growth period,the SPAD values of soybean leaves in uniform planting were higher than those of row planting,which indicated that uniform planting could increase chlorophyll content of soybean and promote photosynthesis of soybean.During V4 R3 R6 period,the net photosynthetic rate（Pn）,leaf area index（LAI）,intercellular CO₂ concentration（Ci）and stomatal conductance（Gs）of soybean leaves in uniform planting were higher than those in row planting,and there was little difference between Pn uniform planting and row planting in soybean leaves at the V4 stage.Moreover,during the V4 period of soybean,the LAI under uniform planting was larger than that in row planting,while the special leaf area（SLA）of soybean leaves in uniform planting were smaller than those in row planting,which indicated that the soybean leaves in uniform planting the was thicker and the photosynthetic area was larger than that in row planting,with the higher Pn value,the uniform planting promoted the photosynthesis of soybean population,which was beneficial to the accumulation of dry matter.（2）Planting pattern had different effects on the contents of nitrogen,phosphorus and potassium in leaves,stem and above-ground part of soybean.in the V5 stage,the potassium content of soybean stems in uniform planting was higher than that in row planting,while the content of phosphorus in soybean stems in uniform planting was higher than that in row planting only at high density.In the R4 stage,the content of nitrogen and phosphorus in the stem of soybean in uniform planting was higher than that in row planting,except for the low density,the content of phosphorus in the stem of soybean in uniform planting was higher than that in the row planting.In the R8 stage,the contents of nitrogen,phosphorus and potassium in the soybean stems were higher than those in the R8 stage except that the content of potassium in the soybean stem in the medium density.In the V5 and R6stages,the content of nitrogen and phosphorus in soybean leaves in uniformly planting were higher than those in row planting.In the V5 stage,except for the low density,the content of potassium in the uniform planting was higher than the row planting.In the R6 stage,the content of potassium in leaves of soybean in the uniform sowing was higher than that in row planting only at the high density.In R8 stage,except that the contents of nitrogen and potassium in soybean seeds in uniform sown at low density were slightly lower than those in row planting,the contents of nitrogen,phosphorus and potassium in soybean seeds at other densities were all higher than those in row planting.Planting pattern had significant effects on nitrogen,phosphorus and potassium in soybean leaves,stems and above-ground total accumulation.During the whole growth period of soybean,uniform planting promoted the accumulation of nitrogen,phosphorus and potassium in stems and leaves,and most notably in V5 stage,the medium density in uniform planting（UM treatment）was the maximum.In R8 stage,the accumulation of nitrogen,phosphorus and potassium of soybean seeds in uniform planting were higher than those in row planting,and the maximum accumulation was occured in the medium density in uniform planting.（3）The planting pattern had a certain effect on the dry matter accumulation of soybean,but the effect was not significant.In all the three planting densities,the dry matter accumulation of soybean in uniform planting was higher than that in planting,which indicated that uniform planting were beneficial to maintain relatively high level of soybean dry matter accumulation.As for yield and quality,the yield in all densities of uniform planting were higher than those in row planting,and the number of seeds per plant,seed weight per plant,hundred seeds weight and yield were higher than those in row planting,and the maximum yield was occurred in the density of 250,000 seeds·hm^-2in the uniform planting,The fat content of the uniform planting pattern was significantly higher than that of the row planting only at low density,and the protein and fat content had no significant differences between the two planting patterns in the other densities.In conclusion,this experiment showed that the uniform planting pattern promoted the dry matter accumulation,photosynthesis and nutrient accumulation of soybean,especially in the early stage of soybean growth,which indicates that the uniform planting is help to soybean absorb nutrients.In terms of yield,uniform sowing with low density(250,000 plants·hm^-2)was the largest yield,and the yield was 3789kg·hm^-2,whichwas7.5%higher than that in the same density in row planting,but there was no significant difference.So,whether the uniform planting pattern is suitable for soybean planting in the first accumulative temperate zone of Heilongjiang Province remains to be further studied.